For each of the situations described, state whether the sampling procedure is simple random sampling, stratified random sampling, cluster sampling, systematic sampling, or convenience sampling. (a) All freshmen at a university are enrolled in 1 of 30 sections of a seminar course. To select a sample of freshmen at this university, a researcher selects 4 sections of the seminar course at random from the 30 sections and all students in the 4 selected sections are included in the sample.

The sampling method applied is Cluster sampling.

Step-by-step explanation:

A cluster sampling method is the type of sampling where first the entire population is divided into homogeneous groups. Then a random sample of these groups are selected.

After selecting a sample of groups, a random sample of fixed size is selected from each group.

In this case all freshmen are first divided into 30 sections, then 4 random sections are selected and the students in those 4 sections are sampled.

The sampling method applied is Cluster sampling.

47 - 90 = 43

43 - 180 = x

x = 137